Process of producing photographs and cinematographic films in natural colors



May 15, 1934. F. UERG 1,958,830

PROCESS OF PRODUCING PHOTOGRAPHS AND CINEMATOGRAPHIC FILMS IN NATURAL COLORS Filed June 12. 1929 Patented May l5, 1934 UNITED STAT/Es PATENT OFFICE AND RAL COLORS TOGRAPIHIC FILMS IN NATU- Friedrlch Lierg, Dresden, Germany Application June 12, 1929, Serial No. 370,321 In Austria August 2, 1928 'z Cmiins.

This invention relates to a process of producing photographs and cinematographic films in natural colors in which two or more insepara- 4bly superposed layers of silver halid emulsions positiveness. e

It is known that difliculties are encountered in obtaining a correct exposure of the partial color traces which are required for subtractive three color photography and also in obtaining an exact covering thereof after conversion into their corresponding colors. It is not new to endeavor to obviate this drawback and methods of working with a plurality of inseparably superposed layers of silver halid of varying color sensitiveness have already been described (see U. S. Patents 1,516,824 and 1,659,148). It was thereby possible to obtain directly by a single exposure and development partial color silver images Jsuperposed in individual layers.

*The present invention resides in the fact that the partial color silver images contained in the two layers of emulsion cast on top of each other are converted only by bath treatmeht into their corresponding colors so that the reactions for producing color are positively conned to the actual layer of emulsion whereby the correctly spectral ground-colors are produced independently of each other. This result is obtained according to thepresent method by separating a layer, after the production of its corresponding color image, from the other layer by gelatinehardening in a physical or chemical manner and thereby shutting off further actions during the` coloration of the superposed partial color image. In order to produce three color images, a third layer of emulsion is preferably provided on the back of the film where the third partial color image is produced. i

In order to produce the color of these two varying ground-colors according to a further very simple mode of carrying out the present process, preferably both partial color images of the double emulsion may be dyed with the same ground-color, rfor instance, bluish red and after shutting'oll the lower partial color image the upper partial color image alone is dyed with a suitable dye, for instance, bluish green so that by mixing both dyes the upper image is dyed correctly spectral its corresponding groundcolor, for instance, pure blue. If an acid dye is used for obtaining a ground-color by redyeing another ground-color while a basic dye has been selected for the uniform preliminary dyeing, it is possible to harden theentire gelatine for shutting off the lower partial color image. The acid we has a great tendency to chemically combine with the basic dye so that in the case of a slight superficial softening of the hardened gelatine, for instance by the addition of acid Vto the coloring bath, the entire upper basic color-image, and this alone, attracts the acid dye.

After dyeing the lower partial color'image, the gelatine is hardened in such a manner that it repels all dye-solutions either by means of physical agents, i. e. in a known manner by light, or in a chemical manner. If substances are used for this purpose, which oxidizeor otherwise tan the gelatine by means oi a chemical bath after the dyeing of the lower partial color image, the said substances are preferably added to a layer (for instance, the light-lter layer) arranged between the two emulsions. However, the two partlal color images can be separated from each other by hardening the\interposed gelatine in a chemical manner by means of the developed silver and without adding any special substances to the gelatine and in the case of emulsions directly cast'on top of each other without any intermediatle layer. The reaction thus taking place as well as the carrying out of the process to produce by means of emulsions cast on top of each other and without any transfer merely by means of baths a positively selection-correctly dyed three-color photography are explained by the following example.

Four examples of the photographic material necessary for carrying out the process are illustrated in cross section and on an enlarged scale on the accompanying sheetof drawings.

Fig. 1 shows an image base 1 provided \with three directly superposed silver halid emulsion layers 2, 3 and 4, which are sensitized for difierent spectral sections.

Fig. 2 illustrates an image base 1 provided on one side with a single emulsion layer 4 and on the other side with a double layer 2, 3.

Figs. 3 and 4 are views similar to Figs. 1 and 2 respectively, in which however the superposed layers are separated by intermediate layers 5.

The following example, in accordance with Pig. 2 describes one way of carrying out this invention.

As already stated, a film emulsied on both sides is'preferably used for taking the picture. l It is thus possible by means of any optional division of the niage for an exposure to take place from both sides and consequently for the time'of exposure to be reduced. Moreover, the dyeing process as well as any desired correction of the obfor, instance in the case of bromide prints.

.e After developing the film and placing the same in 10 an acid bath for interrupting the development, but while the lm is not med, the blue-screen image on one side is dyed according to any convenient method, for instance by toning with vanadium salt and potassium ferricyanide or over a mordant with a yellow dye, and xed before the further treatment of the lm and protected by a coat of varnish, or the film is treated .on one side by merely allowing the same to cat.

Ihe double layer side of the film, in which the red and blue part-image is embedded in the still unvaried silver bromid in the form of black silverimages, is treated, for instance according to the last mentioned mode of gelatine-hardening over developed silver, with a mordant-bath which converts the two silver images into mordant images which combine the basic dyes but cannot be reduced by developing agents. While practically all presently known mordant combinations are reduced to metal by reducing agents such as developing agents, it has been found that a suitable mordant resisting development consists according to process in a silver-copper-sulfocyanid combination, which is produced by bleaching the silver-image in a solution of cupric sulphate and ammonium sulfocyanid to which ammonium oxalate is added. Now if a bluish red dye for instance Rhodamine R index No. 573 is applied this dye attacks the mordant image but not the unchanged silver bromide, because the same does not possess any mordant character. Now the film is exposed to daylight and developed, whereupon the unchanged mordant dye-image is embedded in the black silver. 'I'his silver renders possible a picture-like tanning of the gelatine, such as is known A solution of chromic acid, bromids and cupric sulphate may constitute a suitable bath for this purpose. This bath bleaches the silver-image and at the same time hardens the gelatine at these places, so that the same repel aqueous dyesolutions after being cleared, washed and dried. If the double layer thus treated is allowed to oat on a solution of an acid bluish green dye Afor instance fast green extra bluish index No. 523 or is bathed therein, a picture-like imbibition of the dye takes place inthe known manner at' the unhardenedplaces of the gelatine. Under these circumstances, the said imbibition of the dye can only take place in the mordant image on the surface because all other places are shut olf by the picture-like tanning and repel the color-solution. Consequently, there is produced in the upper layer a pure blue partial image which consists of ^the mingling of the original bluish red dyed mordant magegwith the bluish green imbibition dye image which has only penetrated into the same.

I claimz- 11 A method of producing a lcolor photograph comprising inseparably casting on a base superpcsed silver halid layers' of different color-sensitiveness, expomng said layers, developing where-l by a non-developed space remains between the pertialimages, treating the image layers to give the bottom layer its finish, hardening the nondeveloped part between said/Iayers, and treating 3. A method of producing a color photograph comprising inseparably casting on a base superposed silver halid layers of different color-sensitiveness, exposing said layers, developing whereby a non-developed space remains between the partial images, converting the developed images into special mordant images which are not re- ,ducible by a developing agent, dyeing bluish red the mordant images, now developing the remalned unxed silver bromid, tanning the gela-l tine by a bleaching agent, and redyeing with a bluish green dyestui the top image to produce a pure blue color image. n

4. A method of producing a color photograph comprising casting on a base a silver halid layer,

forming on said layer a separating layer of gelatine, inseparably casting on top of said separating layer" a second silver halid layer of diierent color-sensitiveness, producing the ima ,by a single exposure, developing the partial images, treating the image layers to give the bottom layer its finish, hardening said separating layer, and treating the top layer to give it its nish.

5. A method of producing a color photograph comprising casting on a base a silver halid layer, forming on said layer a separating layer of gelatine, inseparably casting on top of said separating layer a second silver halid layer of different color-sensitiveness casting -a -third silver halid layer of diierent color-sensitiveness on the other side of said base, producing the images by a singler exposure, developing the partial images, treating the image layers to give `the bottom layer its nish, hardening said operating layer, and treating the'top layer to give it its finish.

6. A methodof producing a color photograph comprising casting on a base a silver halid layer, forming on said layer a separating layer of gelatine, inseparably casting on top of said separating layer a second silver halid layer of different color-sensitiveness, producing the images by a single exposure, developing the partial images, dyeing the image layers, hardening said separating layer, and redyeing with a different colored dye the image layer on top of said hardened separating layer. t 1

7. A method of producing a color photograph comprising casting on a base a silver halid layer, forming on said layer a separating layer of gelatine, inseparably casting on top of said separating layer a second silver halid layer of different color-sensitiveness, producing the images by a vsingle exposure, developing the partial' images, dyeing the images bluish red, hardening said separating layer, and treating with a bluish green dyestui the image on top of said hardened separating layer to produce a pure blue color Image. 

